1. Field of the Invention
The present invention relates to an image display apparatus and a method of displaying an image, and more particularly, to an apparatus having a lower data transmission rate and less degradation of the image quality for displaying data with a lower data-rate depending on the state of a communications network and a method therefor. The present application is based on Korean Patent Application No. 00-31951, which is incorporated herein by reference.
2. Description of the Related Art
The next generation mobile communications system, the international mobile telecommunications IMT-2000, can provide image transmission services in addition to voice and text services using commonly used portable personal information terminals. Image transmission of the IMT-2000 includes storing and transmitting still and moving images according to international standards of digital image compression such as H.263 or MPEG4.
When encoding an image by H.263, input image signals formed of frames (progressive images) are inputted to a discrete cosine transform (DCT) treater (not shown), and the DCT treater treats the progressive image with DCT as a divided block unit of 8xc3x978 size, and inputs the DCT coefficient of the frequency region to a quantization device (not shown). The quantization device quantizes and compresses the DCT coefficient according to the quantization interval controlled by the fixed amount of bits per frame. The signals quantized by the quantization device are transmitted through the network, through movement compensation and prediction processes after inverse quantization and inverse discrete transformation.
Such a conventional moving image encoding process enables the state of the communications network to be determined through a real-time transport protocol (RTP) or a real-time control protocol (RTCP). Then, if there is much traffic, the value of the quantization factor is controlled as a result of the rate control in order to decrease the amount of the transmitted bits. By doing this, the image quality is degraded excessively just as the screen size is maintained.
To solve the above problems, it is an object of the present invention to provide an apparatus with a lower data-rate and less degradation of the image quality by shrinking the screen size and transmitting reduced-size screen data depending on the state of a communications network.
It is another object of the present invention to provide a method for enabling a lower data-rate and less degradation of the image quality by shrinking the screen size and transmitting reduced-size screen data depending on the state of a communications network.
Accordingly, to achieve the above objects, there is provided an apparatus having a lower data-rate and less degradation of the image quality, wherein an apparatus for transmitting and receiving data through a communications network, preferably includes: a screen size determining means for determining the screen size of image signals input according to control signals; an image signal encoding means for encoding the image signals according to the determined screen size; a control means for outputting control signals which determine the screen size by evaluating the state of the communications network and for transmitting the encoded image signals through the communications network; an image signal decoding means for decoding the image signals transmitted through the communications network; and a display means for displaying the decoded image signals.
Further, the apparatus of the present invention having a lower data-rate and less degradation of the image quality, wherein an apparatus for transmitting and receiving data through a communications network, preferably includes: a screen size determining means for determining the screen size of image signals input according to control signals; an encoding means for encoding the image signals according to the determined screen size; a control means for outputting control signals which determine the screen size by evaluating the state of the communications network and for transmitting the encoded image signals through the communications network by setting the bits for determining a prescribed screen size; a decoding means for magnifying and decoding the image signals transmitted through the communications network as the image signals of the initial screen by perceiving the existence of the setting of bits for determining the transmitted screen size; and a display means for displaying the decoded image signals.
To achieve another object of the present invention, there is provided a method for enabling a lower data-rate and less degradation of the image quality, preferably, including: (a) determining the screen size of the image signals input into the communications network; (b) encoding the image signals according to the screen size determined in the step (a), and transmitting the image signals to the communications network; (c) decoding the image signals according to the screen size transmitted through the communications network; and (d) displaying the decoded image signals.
Also, the method for enabling a lower data-rate and less degradation of the image quality includes: (a) determining the screen size of image signals input to the communications network; (b) encoding the image signals according to the screen size determined in the step (a), setting and transmitting the prescribed bits for determining the screen size to the communications network; (c) magnifying and decoding the image signals transmitted through the communications network as the image signals of the initial screen by perceiving the existence of the setting of bits for determining the transmitted screen size; and (d) displaying the decoded image signals.